eigenmann: the cheirodontin^. 63 



suborbital with a wide naked area around its entire border. Postorbital covering 

 nearly the entire postorbital space. Mouth moderate, the maxillary not reaching 

 to the end of the second suborbital; adipose fin well developed; caudal naked; 

 lateral line short; frontal fontanel large, entirely separating the frontals; no pseudo- 

 tympanum; no prominent interhsemals. 



33. Mixobrycon ribeiroi (Eigenmann). (Plate X, fig. 2.) 

 Cheirodon ribeiroi Eigenmann, Proc. U. S. Nat. Mus., Vol. XXXIII, 1907, p. 9; 



Reports Princeton Univ. Exp. Patagonia, Vol. Ill, 1910, p. 429. 



10229, 1. U. M., one, type, 35 mm. to base of caudal. Puerto Max, Paraguay, 

 J. D. Anisits. 



This species is known only from the type. 



Head 3.4; depth 3; D. 11; A. 26; scales 5-33-4, seven scales with pores. 

 Eye 2.5 in the head, greater than interorbital. 



Compressed, elongate; preventral area rounded; predorsal area rounded, with 

 a median series of eleven scales; occipital process elongate, pointed, reaching one- 



FiG. 20. Dentition of Mixobrycon ribeiroi Eigenmann. 



fifth to dorsal, bordered bj^ three scales on each side; frontal fontanel long, pointed, 

 1.5 in the parietal; maxillary long, slender, nearly three-fourths as long as eye; 

 premaxillary with four large, heavy teeth; the second tooth largest, with seven 

 points, the middle point of which is the largest, the base of the tooth much nar- 

 rower than the tip; the second to fourth teeth graduate; no teeth on the maxillary; 

 mandible with four, heavy, five-pointed, graduate teeth; teeth of side of jaw lost 

 or absent; second suborbital with a wide naked area around its entire margin. 

 Gill-rakers 7 -|- 11, the longest about one-third as long as eye. 



Origin of dorsal very nearly equidistant from tip of snout and caudal; origin 

 of anal under back part of dorsal; only one interhsemal (or none?) on the caudal 

 peduncle; pectorals reaching ventrals, the latter not to anal; adipose fin well- 

 developed. 



